This invention relates generally to granulation apparatus. More specifically, it pertains to apparatus present on the beater means to prevent the loss of the product to be granulated from the end walls of the granulator housing.
Granulators have been used for a number of years to reduce the size of particles. Generally, the particle reduction has taken place by forcing the particles through a screen with a plurality of holes of predetermined size and shape. The forcing of the particles through the holes can be done by either a hammer mill that has a rotatable shaft with radially extending hammers projecting therefrom or a rotatable shaft with radially projecting spaced blades mounted to the shaft. The rotatable shafts may be oriented either horizontally or vertically.
Most granulators that have been used to process chemical compounds wnich are formed in preformed flakes or moist rolls, such as calcium hypochlorite, utilize a generally horizontally extending rotatable shaft. In such a granulator, the granulated particles pass from the granulator into some type of a dryer where the particles are heated until the desired moisture level is obtained. The particles, however, once they pass through the granulator, are predetermined sized grains. What has not passed through the granulator screen is generally a fine particle that can be referred to as dust, or oversized particles needing further granulation. In prior granulators utilizing a generally horizontally extending rotatable shaft for calcium hypochlorite, these fine grains or dust particles tend to move outwardly on the beater means attached to the rotatable shaft and exit at the shaft junction in the end walls of the granulator housing. This results in considerable loss of chemical compound, as well as clogging between the end wall housing and the beater means flanges, and, because of the corrosive nature of the calcium hypochlorite, the possible accelerated corrosion of the granulator components at this critical location.
Attempts to seal this junction of the beater means flanges and the end walls have used ring members and flanges to provide a sealing surface in conjunction with a separate sealing member and the flanges. However, this design creates frictional heating between the ring members and the flanges which promotes product decomposition and accelerates component corrosion. To reduce the heat build-up, the sealing members have been removed , and the clearance between the ring members and flanges reduced. However, there is still some clearance through which the product particles will escape and eventually pass through the end walls of the granulator.
The foregoing problems are solved in the design of the present invention by providing a means to force the granular particles engaged by the beater means back to the central portion of the beater means away from the shaft ends mounted in the end walls of the housing.